Plastic compositions containing caprylic acid esters



Patented Mar. 27, 1945 PLASTIC COMPOSITIONS CONTAINING CAPRYLIC ACID ESTERS Frank A. Strauss, New Brighton, Staten Island, N. Y., assignor to Wecolinc Products, Inc., Boonton, N. J a corporation of New Jersey No Drawing. Application November 28, 1940, Serial No. 367,672

Claims.

The present invention is directed to plastic compositions containing plasticizing materials of a novelcharacter. This application is a continuation-in-part of my co-pending application Serial No. 199,673, filed April 2, 1938, entitled Esters of caprylic acid and compositions containing the same."

More specifically, the present invention comprises compositions containing certain esters of fatty acids having eight carbon atoms. The esters are made with certain polyhydroxy alcohols, specifically, diethylene glycol and triethylene glycol, and the corresponding propylene glycols. It has been found that the esters of the triethylene glycol are particularly adapted for the purpose and are in general superior to those made with diethylene glycol. The fatty acid component of said esters may be certain of the saturated fatty acids or isomers thereof. Preferably, because of the ease of obtaining same, I prefer to use the natural fatty acid, namely, caprylic.

Various esters have previously been proposed for plasticizing p ses, among which was the stearic acid ester of triethylene glycol. It was intended that this product be added to nitrocellulose compositions. However, this product is a hard, white solid at ordinary temperatures, and although it may be mixed with nitrocellulose, it is of limited compatibility therewith. In other words, such plasticizer dissolves only slightly in the nitrocellulose composition, so that if more than a small quantity thereof is used in a nitrocellulose solution, upon drying the product separates out and produces a frosty, non-transparent appearance.

It has also been proposed to provide a plasticizer of the vegetable oil type in which a lower fatty acid, such as acetic or propionic acid, was introduced into the glyceride esters. Products of this kind are, of course, quite different from those described and claimed herein.

If one should attempt to make the diethylene glycol ester of a lower fatty acid such as acetic or propionic, a low melting point compound is obtained which has plasticizing effects. However, such compounds are definitely volatile and, therefore, compositions made therewith tend to become brittle on ageing. Since plasticized compositions are intended to be more or less permanent, the use of a plasticizer which has an appreciable vapor tension is impractical. Moreover, the water resistance of such compounds is poor.

The present invention utilizes saturated fatty acids having eight to ten carbon atoms and esterifies them in order to produce neutral esters with diethylene glycol, triethylene glycol, and the propylene glycols. It has been found that these esters or mixtures thereof do not have the disadvantages of the esters of higher fatty acids in that they will blend in practically all proportions with base compositions. They do not have the disadvantages of the esters of lower fatty acids in that they are non-volatile and are permanent in the compositions and have better water resistance.

While the invention is capable of embodiment in various forms, the following specific examples will illustrate a few of the many compositions which may be made in accordance with the present invention.

Example I A mixture is made of 300 grams of caprylic acid obtained by the fractional distillation of the mixed fatty acids of cocoanut oil and containing approximately 97% of caprylic acid with very minor amounts of other fatty acids of cocoanut oil, and 100 grams of diethylene glycol. The mixture is placed in a container, heat is applied, and a gentle stream of carbon dioxide is passed through the same. The temperature is gradually raised over a period of three hours up to about 270 C., at which point it is held for several hours while causing a stream of carbon dioxide to pass through the same, in order to distill ofi any excess of fatty acid which may be presentx The resulting product is a pale, straw colored oil.

It is then washed with very dilute caustic soda solution, after which it is washed several times with distilled water. The oil is filtered to remove as much as possible of the suspended water, and is then heated to 90 C. under vacuum to remove the remainder of the water. It is bleached with activated carbon and bleaching earth at about C. for one-half hour, filtered, and the bleaching and filtering operations are repeated if necessary until the color is discharged.

The refined product, which is a pale limpid oil, is substantially insoluble in water, but is miscible with practically all of the usual lacquer solvents and diluents in all proportions. One part of the refined product is mixed with three parts of low viscosity nitrocellulose, and is thoroughly incorporated in the same by conducting th mixing on hot rolls.

Erample II There is provided grams of a mixture of diethylene glycol and triethylene glycol in equal proportions. To this is added 300 grams of a fraction of distilled cocoanut oil fatty acids, composed principally of about 85% caprylic acid and small amounts of adjacent acids, that is, the acids next to caprylic and having even numbers of carbon atoms, and having an acid number of about 383. The mixture is heated in the presence of a gentle stream of carbon dioxide for over three hours, the temperature being gradually increased until about 270 to 275 C. is reached, at which temperature the mixture is held for about one hour while passing a current of carbon dioxide through the same. The mixture is purifled, as stated above, and the properties of the product are quite similar to the product of Example I.

A mixture is made of 40 parts by weight of this ester with 60 parts by weight of low viscosity ethyl cellulose (6.5 sec.) The ingredients are heated and compounded in a suitable mill until the mixture is uniform.

Example III 140 grams of triethylene glycol are mixed with 300 grams of a mixture consisting essentially of about 90% of caprylic acid and the remainder caprlc acid. A reaction is caused to take place following the procedure set forth in Example II.

3 parts by weight of the mixed ester is incorporated in '7 parts by weight of a polyvinyl resin. Specifically, the resin'used is of the aldehyde modified polyvinyl acetate, and commonly termed vinyl acetal resin, wherein a condensation was caused to take place between polyv yl alcohol and butyraldehyde. The mixture is formed on hot rolls and is extruded into sheets for use.

The products of the present invention are compatible with nitrocellulose in solution and in dried films in all proportions up to at least 3 parts of plasticizer to 2 of nitrocellulose. The dried films show no tendency to sweat, spew or separate out theplasticizer even when baked at 200 F. A ratio of plasticizer to nitrocellulose of less than one to two is sufficient to give films of great distensibility and pliability. At the same time, nitrocellulose will tolerate very large additions of the plasticlzer without becoming sticky or tacky. A film containing these products and nitrocellulose in the ratio of three to two, while very soft and distensible, is only slightly tacky. A fllm containing tricresyl phosphate in the same proportions is a sticky semi-solid coating. The permanency and non-volatility of these products are among their most valuable characteristics. A nitrocellulose film containing 33% of the products of the present invention subjected to a temperature of 220 F. for 18 hours will show a. negligible shrinkage and no loss of flexibility. A film plasticized with tricresyl phosphate subjected to the same conditions shows appreciable shrinkage and embrittlement, while when dibutyl phthalate is used as plastioizer, this treatment results in severe shrinkage and embrittlement, indicating loss of plasticizer.

The products of the present invention are characterized in that they are compatible with nitrocellulose, in all proportions at room temperatures within the limits above stated. They have extremely low vapor pressures and a negligible volatility. The odor is almost negligible but pleasant, and the color is very light. They are inert to atmospheric oxidizing conditions and are not decomposed or changed by light. They have strong softening and plasticizing action, and a low specific gravity.

This material is particularly adapted for use in flexible coatings. For these purposes it has the virtues of a true solvent plasticizer tor nitrocellulose, compatibility, chemical inertness and neutrality, without the tackiness which sometimes results when large quantities of solvent plasticizer are used to get a flexible him. At the same time, it exhibits the good qualities of the plasticizers of the vegetable oil type, giving flexible pliable him; without tendency to ,tackiness, yet not having the bad odor, poor color, susceptibility to oxidation and sweating tendencies which many of thes oil plasticizers often have.

Among the valuable compositions made in accordance with the present invention are those capable of use in the making of safety glass. For instance, a composition 01' the triethylene glycol ester of caprylic acid with a polyvinyl resin constituting the inner layer between'two sheets of glass, has proved to be highly effective for safety purposes. The adhesion of the layer to the glass was very high at wide ranges of temperature, so that at 120 F. and all the way down to -20 F. the adhesion was perfect. Also, the strength of the material is highly satisfactory over the entire range, and standard impact tests have proven that a laminated plate, although completely shattered by blows, nevertheless still adheres together without any scattering of broken pieces of glass.

This is of extreme importance to the automotiveand other industries.

Compositions made in accordance with the present invention have low vapor tensions at high temperatures, so that there is no deterioration of the composition by loss of plasticizer. The compositions are durable and resistant to moisture. Th esters of the present invention are compatible in very wide ratios with most of the organic thermoplastic materials. While the caprylic acid is the major acid constituent of the esters, the amount of capric acid which may be mixed therewith may be up to the ratio of 8 to 2, that is the caprylic acid content may be as low as of the acids present.

In the above examples, fractions of the naturally occurring fatty acids obtained from cocoanut oil were used. These fractions, while consisting of mixtures of fatty acids mentioned above,

also may contain small proportions of their higher and lower homologues. For some purposes the use of substantially pure fatty acids is preferable, as the presence particularly of fatty acids of higher molecular weight, whose esters have higher melting points and lower solubilities, is undesirable. In such cases, caprylic or capric acid or the like, of a high degree of purity, may be used. Such acids may be obtained from the fatty acids of naturally occurring fats by careful fractional distillation or they may be prepared by synthetic methods.

While I have described my invention setting forth several specific embodiments thereof, it will be quite apparent that variations may be made in the details of the practice of the invention. Other methods of forming the esters may be used, although I have found the method described herein to be simple and effective. Instead of the natural fatty acids of 8 and 10 carbon atoms, the synthetic saturated fatty acids and isomers thereof may be used. The specific examples given were set forth for purposes of illustration only, and it is quite apparent that any one of the acids named may be combined with any of the glycols named, or that mixtures of two or more of the acids may be reacted with one of the glycols, or the acids may be reacted with mixtures of said glycols.

Compositions with various other resins than specifically named above may be made with good advantage. For instance, the esters may be incorporated with the acrylate resins, with various cellulose esters and ethers, with phenol-formaldehyde, urea-iormaldehyde,,modifled alkyd resins, and the like. Other glycols, as, for example, trimethylene glycol, may be used. The proportion of esters in the composition to be plasticized may vary within a wide range, as for example, between 25 and 50 percent. In many cases, 33% has been found to be eminently suitable.

In the claims appended hereto limitations are contained to caprylic acid. It is to be understood that this term includes not only the pure caprylic acid, but also a caprylic acid mixture containing minor amounts of other fatty acids.

What I claim is:

l. A composition 01 matter adapted for application as the plastic layer of a safety glass structure comprising a vinyl acetal resin having uniiormly incorporated therein as a plasticizer a minor proportion of the substantially neutral mixed esters oi a fully esterifled polyalkyiene glycol with a mixture of caprylic and capric acids, 4

said acids being -in the proportion of about 80-90% of caprylic and 20-10%- of capric, said composition being strong and adherent to glass at high and low temperatures.

2. A composition of matter adapted for application as the plastic layer of a safety glass structure comprising a vinyl acetal resin having uniformly incorporated therein as a plasticizer a minor proportion of the substantially neutral mixed esters of a, fully esteriiied polyalkylene glycol with a mixture of caprylic and capric acids, said acids being in the proportion of about 80-90% of caprylic and 20-10% of capric, the proportion of plasticizer to resin being about 25-50%, said composition being strong and adherent-to glass at high and low-temperatures.

' 3. A composition of matter adapted for application as the plastic layer of a safety glass structure comprising a vinyl acetal resin having uniiormly incorporated therein as a plasticizer a minor proportion of the substantially neutral mixed esters of a fully esterified mixture of at least two polyalkylene glycols with a mixture of caprylic and capric acids, said acids being in the proportion of about 80-90% of caprylic and 20-10% of capric, said composition being strong and adherent to glass at high and low temperatures.

4. A composition of matter adapted for application ag the plastic layer of a safety glass structure comprising a vinyl acetal resin having unliormly incorporated therein as a plasticizer a minor proportion of the substantially neutral mixed esters of a fully esterifled tripropylene glycol with a mixture oi. caprylic and capric acids, said acids being in the proportion of about 80-90% oi caprylic and 20-10% of capric, said composition being strong and adherent to glass at high and low temperatures.

5. A composition of matter adapted for application as the plastic layer of a safety glass structure comprising a vinyl acetal resin having uniiormly incorporated therein as a plasticizer a minor proportion of the substantially neutral mixed esters of a fully esterified triethylene glycol with a mixture of caprylic and capric acids,

said acids being in the proportion of about 80-90% of caprylic and 20-10% oi capric, said composition being strong and adherent to glass at high and low temperatures.

FRANK A. STRAUSS. 

